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Proceedings Paper

Dynamic MEMS devices for multiaxial fatigue and elastic modulus measurement
Author(s): Carolyn D. White; Rui Xu; Xiaotian Sun; Kyriakos Komvopoulos
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Paper Abstract

For reliable MEMS device fabrication and operation, there is a continued demand for precise characterization of materials at the micron scale. This paper presents a novel material characterization device for fatigue lifetime testing. The fatigue specimen is subjected to multi-axial loading, which is typical of most MEMS devices. Polycrystalline silicon (polysilicon) fatigue devices were fabricated using the MUMPS process with a three layer mask process ground plane, anchor, and structural layer of polysilicon. A fatigue device consists of two or three beams, attached to a rotating ring and anchored to the substrate on each end. In order to generate a sufficiently large stress, the fatigue devices were tested in resonance to produce a von Mises equivalent stress as high as 1 GPa, which is in the fracture strength range reported for polysilicon. A further increase of the stress in the beam specimens was obtained by introducing a notch with a focused ion beam. The notch resulted into a stress concentration factor of about 3.8, thereby producing maximum von Mises equivalent stress in the range of 1 through 4 GPa. This study provides insight into multi-axial fatigue testing under typical MEMS conditions and additional information about micron-scale polysilicon mechanical behavior, which is the current basic building material for MEMS devices.

Paper Details

Date Published: 16 January 2003
PDF: 12 pages
Proc. SPIE 4980, Reliability, Testing, and Characterization of MEMS/MOEMS II, (16 January 2003); doi: 10.1117/12.476332
Show Author Affiliations
Carolyn D. White, Univ. of California/Berkeley (United States)
Rui Xu, Univ. of California/Berkeley (United States)
Xiaotian Sun, Univ. of California/Berkeley (United States)
Kyriakos Komvopoulos, Univ. of California/Berkeley (United States)

Published in SPIE Proceedings Vol. 4980:
Reliability, Testing, and Characterization of MEMS/MOEMS II
Rajeshuni Ramesham; Danelle M. Tanner, Editor(s)

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